Difficulty in reaching working length
Under normal conditions, working length should be reached during the first 30 seconds of operation. If you are unable to reach working length within 60 seconds in any of the in-bound pecking strokes, stop and follow these steps:
- Make sure that the shaft of the SAF does not engage the access cavity walls; this might happen in incisors or premolars that present exceptionally small pulp chambers and/or access cavities. If so, use an SAF with a longer active portion and make sure it does not buckle. Further enlargement of the access cavity is usually not necessary.
- Make sure that your coronal orifice preparation is adequately flared and that you have an unobstructed straight access to the canal. Use the Pre-SAF OS rotary instrument if needed.
- Verify the adequacy of the glidepath by manually inserting the SAF to working length. If the SAF cannot be inserted freely, realign the SAF, by rotating it by 90 degrees when it is not engaged with the canal walls, and re-insert it into the canal. You may need to repeat this realignment up to 4 times, and if this still does not allow to insert the SAF to working length - re-establish the glidepath using the Pre-SAF 2 rotary instrument.
- Make sure that the canal is clear of gross pulp tissue remnants .
- Make sure that the length of the active part of the SAF is at least equivalent to the length of the canal from the canal orifice to working length.
- Do not attempt to force the SAF to working length. Such attempts will result in buckling and damage to the file.
- Use EDTA lubricant
File breakage & file seperation
Unlike rotary instruments, the SAF’s lattice-like design allows it to partially tear without separating completely (see top figure). This safety feature greatly reduces the risk of file separation. If you encounter frequent file breakages despite using the file in accordance with its specifications, please check the following:
1. Make sure that the access cavity offers an unobstructed straight line access to the canals.
2. Make sure your glidepath allows the SAF to reach working length freely.
3. Make sure to operate the SAF according to the vertical axis of the canal, and operate it in pecking motions in the vertical axis only, without any brushing or circumferential motions.
Insufficient glidepath, improper vertical axis operation or indirect access to the canal may lead to buckling of the file (bottom figure) and subsequent file damage.
4. Stretch or loosen the irrigation tube connected to the file to control the amount of rotation required – higher rotation speed may increase the risk of mechanical damage, whereas lack of rotation may not allow the required circular repositioning of the file during the pecking motions.
5. Make sure to lubricate the RDT3 handpiece head after each use; lack of proper lubrication may increase the head torque values.
Excessive pressure and increased rotation speed will create a torsional stress on the file and should be avoided.
6. In the rare case of complete file separation (chance of 0.6% or less according to a Solomonov et al., J Conserv Dent, 2015), use a Hedström file to remove the separated segment. It is usually an easy procedure that does not require any additional removal of dentin, as opposed to separated rotary or reciprocating file that is usually screwed into the dentin wall of the canal.
